I thought we got 75%?

I'm just trying to understand how the steemit system works. Everything I've read says authors get a minimum of 75% of the steem dollar amount made by posts. But when I look at other people's payouts, it's closer to 50%.

For example, here is a payout

Past Payouts $2.02

• Author $1.74
  (0.87 SBD, 0.22 SP)
• Curators $0.28

Author is suppose to receive $1.74 steem dollars. But what is received is 0.87 + 0.22, totaling $1. Where has the other 74c gone? Will that be paid out later?

Also another question I have, I've read that the steem dollar is suppose to parity the USD, but it seems to be strayed away and is now worth more in USD than STEEM. Can anyone explain why this has happened? Are there any pro's/con's? Does that mean the original purpose of steem dollars pointless?

Any info is appreciated, just trying to wrap my head around all this, Cheers